Wood treated with chromated copper arsenate has that familiar pale green colour to it. While CCA is green, copper oxide is reddish brown or black, depending on the oxidation state. (The green or blue copper isn't the result of oxidation, but rather the result of salt formation, usually a carbonate or chloride salt, but in this case, an arsenate salt).
The real question here is whether CCA would react in such a way as to form red-brown cuprous oxide if left in contact with human skin. I can't say that it wouldn't.
The red flag for me is that copper's an easy metal to do a qualitative test for, and I'd expect a police chemist to have caught it if the body had been drenched in a copper compound.